Fixing device for fixing toner on sheet by heating toner, and image forming apparatus including fixing device

Abstract

A secondary coil is attached to an end portion of a heating film. A space is formed inside a core member. A primary coil, which generates a magnetic field that causes the secondary coil to generate a current by electromagnetic induction, is arranged inside the space together with the secondary coil.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]The present invention relates to a fixing device for fixing toner on a sheet by heating the toner, and an image forming apparatus including the fixing device.[0003]2. Description of the Related Art[0004]An image forming apparatus of an electrophotography scheme or electrostatic recording scheme includes a fixing device used to fix an unfixed toner image formed on a sheet. According to Japanese Patent Laid-Open No. 06-202513, a fixing device, in which a heat generation layer is provided to a fixing film itself, and which supplies a current to this heat generation layer to directly heat the fixing film so as to heat and fix a toner image, has been proposed. This fixing device has merits of a short time period required from the beginning of power supply until a fixable state is reached, and a small power consumption amount. However, since the fixing device of Japanese Patent Laid-Open No. 06-202513 supplies electric power ...

AI Technical Summary

Benefits of technology

[0008]A feature of the present invention is to reduce a rotation load of a rotatable heating element, to reduce deformation of the rotatable heating element, and to realize efficient electric power transmission from a primary coil to a secondary coil.

Problems solved by technology

This fixing device has merits of a short time period required from the beginning of power supply until a fixable state is reached, and a small power consumption amount.

However, since the fixing device of Japanese Patent Laid-Open No. 06-202513 supplies electric power to the heat generation layer using a brush electrode, it readily causes heat generation unevenness in a circumferential direction of the fixing film.

This is caused by a wear of the electrode due to a sliding contact and an oxide layer formed upon discharging.

However, in the fixing device of Japanese Patent Laid-Open No. 2002-123113, since a ferrite core included in a fixing roller rotates together with the fixing roller, a rotation load on the fixing roller becomes heavier.

Furthermore, when the fixing roller is made of a flexible film-like member, the ferrite core as a load causes deformation such as torsion in the film.

When such problem is to be solved by increasing the rigidity of the film, a heat capacity of the film is increased, resulting in demerits in terms of a time period from the beginning of power supply unit a fixable state is reached, and power consumption.

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